A drive electrode to which a voltage for allowing a vibrator to vibrate is applied and first and second detection electrodes extending in the longitudinal direction of the vibrator in parallel to each other are formed as the upper electrode such that the drive electrode is interposed between the first and second detection electrodes and does not contact with the detection electrodes. In the case where there is a difference between the detection signals detected in the first and second detection electrodes when a voltage is applied between the lower electrode and drive electrode to allow the vibrator to vibrate at a vertical resonance frequency, a laser light is irradiated to a desired portion of the vibrator to apply grinding operation based on detection signals detected in the first and second detection electrodes, thereby adjusting the shape of the vibrator.